I am having problems backing up a few min of video to a USB drive. My NVR is Samsung SRN-1673S

The external USB flash drive is instantly recognized. After I choose the date, time and cam the OK button at the bottom is still greyed out.

There is also a drop down menu next to TYPE giving me the option of NVR or SEC Iíve tried both and still the ok button is greyed out.

I have also tried using several USB flash drives using FAT32. This is the format Samsung says to use. The book also says to use a Samsung or Sandisk flash drive. I don't have these brand USB flash drives at the moment though the NVR reads the capacity of the USB drive and will even format from the NVR menu. Anyone have this issue before? Thank you!